Amino acid analogs activate NF-kappaB through redox-dependent IkappaB-alpha degradation by the proteasome without apparent IkappaB-alpha phosphorylation. Consequence on HIV-1 long terminal repeat activation.
We report here that amino acid analogs, which activate hsp70 promoter, are powerful transcriptional activators of human immunodeficiency virus 1 (HIV-1) long terminal repeat (LTR), an activation which was impaired when the two kappaB sites present in the LTR were mutated or deleted. Amino acid analogs also stimulated the transcription of a kappaB-controlled reporter gene. Upon treatment with amino acid analogs, the two NF-kappaB subunits (p65 and p50), which are characterized by a relatively long half-life, redistributed into the nucleus where they bound to kappaB elements. This phenomenon, which began to be detectable after 1 h of treatment, was concomitant with the degradation of the short lived inhibitory subunit IkappaB-alpha by the proteasome. However, contrasting with other NF-kappaB inducers that trigger IkappaB-alpha degradation through a phosphorylation step, amino acid analogs did not change IkappaB-alpha isoform composition. Antioxidant conditions inhibited amino acid analog stimulatory action toward NF-kappaB. This suggests that aberrant protein conformation probably generates a pro-oxidant state that is necessary for IkappaB-alpha proteolysis by the proteasome. Moreover, this activation of NF-kappaB appeared different from that mediated by endoplasmic reticulum overload as it was not inhibited by calcium chelation.
Kretz-Remy
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Laboratoire du Stress Cellulaire, Centre de Génétique Moléculaire et Cellulaire, CNRS-UMR 5534, Université Claude Bernard Lyon-I, 69622 Villeurbanne Cedex, France.
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D000596:Amino Acids / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology; D001384:Azetidines / Q000494:pharmacology; D002172:Canavanine / Q000494:pharmacology; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005979:Glutathione Peroxidase / Q000378:metabolism; D016325:HIV Long Terminal Repeat / Q000187:drug effects*; D015497:HIV-1 / Q000235:genetics; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D020672:I-kappa B Proteins; D009097:Multienzyme Complexes / Q000378:metabolism*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D010084:Oxidation-Reduction; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D046988:Proteasome Endopeptidase Complex; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000235:genetics
D000596:Amino Acids; D000975:Antioxidants; D001384:Azetidines; D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; D020672:I-kappa B Proteins; D009097:Multienzyme Complexes; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D000072000:NF-KappaB Inhibitor alpha; C082735:azetidine; D002172:Canavanine; D005979:Glutathione Peroxidase; D015500:Chloramphenicol O-Acetyltransferase; D001616:beta-Galactosidase; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex